This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Clinical trials to study the pharmacokinetics of antiretroviral drugs in pregnant women are limited. The development of appropriate dosing regimens for the pregnant woman is critical to the health of both mother and fetus. Overdosing may lead to maternal adverse events and increased risk of fetal toxicity. Underdosing may lead to inadequate virologic control, increased risk of developing drug resistance mutations and a higher rate of perinatal HIV transmission. Both increased metabolism and suppressed immunologic response during pregnancy can leave the mother at risk for viral breakthrough and progression of disease. Independent of pharmacologic factors, pregnant women may be at particular risk for progression of their HIV disease. Pregnancy produces a temporary physiologic and immunologic homeostatis between tissues that are antigenically different. In order to accommodate the fetus, the maternal immune system is at least partially suppressed with an elevation of glucocorticoids (implicated in inducing hepatic metabolism) as one component of this response. Primary Objective: To describe the PK parameters during pregnancy of selected antiretroviral drugs currently used in the clinical care of pregnant HIV-infected women, and to determine if therapeutic dosing regimens of these antiretroviral drugs produce adequate drug exposure during pregnancy compared to a) historical data from non-pregnant adults;and b) the same women in the study cohorts during the postpartum period. Secondary Objectives: To compare antiretroviral drug concentrations is plasma from cord blood with those in maternal plasma at the time of delivery. To indirectly assess the induction of cytochrome P450 3A4 by determining the ratio in urine of 6B-hydroxycortisol to cortisol.